U.S. patent number 6,086,611 [Application Number 08/937,199] was granted by the patent office on 2000-07-11 for bifurcated stent.
This patent grant is currently assigned to AVE Connaught. Invention is credited to Maria Carleton, James Cattabriga, James Duffy, Naill Duffy, Gigliano Garutti, Daniele Manara.
United States Patent |
6,086,611 |
Duffy , et al. |
July 11, 2000 |
Bifurcated stent
Abstract
An endoluminal stent is formed in a modular construction to
include at least one elongate spine and a plurality of general
tube-defining modules attached to the spine, or spines, in a
longitudinal array. The modules are constructed along a spine-like
structure so as to form a bifurcate shape for implantation in
branching or bifurcating vessels. Each module defines, in
cooperation with a spine, a closed ring-like structure. Each of the
modules is radially expandable from a reduced diameter, low profile
configuration, in which it is readily navigated through the body
passages, to an expanded diameter engageable with the inner luminal
surface of the body lumen. The stent, being of modular
construction, can be built to individual specifications for a
specific patient. Modules are formed from a wire shaped in a flat
serpentine configuration that is then wrapped in a cylindrical
configuration with its free ends connected to a spine. The modules
are expandable, as by a balloon, from a low profile to an expanded
configuration. During expansion, the modules can wipe against the
inner surface of the lumen to smooth sharp points or edges. A spine
of the stent defines a substantially greater mass than that of the
individual modules such that the spine can be readily observed
under X-ray or fluoroscopy. The modular construction enables a wide
range of variation in the characteristics of the stent, including
longitudinal flexibility, radial expansion characteristics, among
others.
Inventors: |
Duffy; Naill (Tuan,
IE), Carleton; Maria (County Galway, IE),
Manara; Daniele (Bentivoglio, IT), Garutti;
Gigliano (Poggio Renatico, IT), Cattabriga; James
(Bologna, IT), Duffy; James (Trim, IE) |
Assignee: |
AVE Connaught (Dublin,
IE)
|
Family
ID: |
25469618 |
Appl.
No.: |
08/937,199 |
Filed: |
September 25, 1997 |
Current U.S.
Class: |
623/1.35 |
Current CPC
Class: |
A61F
2/82 (20130101); A61F 2002/065 (20130101); A61F
2/954 (20130101) |
Current International
Class: |
A61F
2/06 (20060101); A61F 002/06 () |
Field of
Search: |
;623/1,12 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 421 729 |
|
Apr 1991 |
|
EP |
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0 669 114 |
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Aug 1995 |
|
EP |
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WO 95/21592 |
|
Aug 1995 |
|
WO |
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WO 96/41592 |
|
Dec 1996 |
|
WO |
|
Primary Examiner: Milano; Michael J.
Attorney, Agent or Firm: Sterne, Kessler, Goldstein &
Fox P.L.L.C.
Claims
What is claimed is:
1. A bifurcated stent comprising:
a main body comprising a support wire and a plurality of modules
coupled to said support wire at sequential locations along said
support wire, said support wire extending between and through said
plurality of modules;
a first side branch coupled to said main body, said first branch
comprising at least one module coupled to a support wire; and
a second side branch coupled to said main body, said second side
branch comprising at least one module couple to a support wire,
wherein said first side branch and said second side branch are
coupled to each other at an apex section of the bifurcated stent
and the bifurcated stent is inserted into a body lumen in a closed
configuration with an axis of said first side branch and an axis of
said second side branch substantially parallel to each other.
2. A bifurcated stent as defined in claim 1, wherein each of said
modules defines a closed circumferential loop and said modules are
arranged on said respective support wire to define a generally
tubular configuration.
3. A bifurcated stent as defined in claim 1, wherein each of said
modules is expandable from a radially contracted configuration in
which it can be positioned in the body lumen to a radially expanded
configuration.
4. A bifurcated stent as defined in claim 1, wherein each of said
modules is formed from a serpentine wire having a plurality of
elongate segments alternated with shorter connective bends.
5. A bifurcated stent as defined in claim 4, wherein said
serpentine wire has free terminal ends attached to a connector to
secure each of said modules in its closed circumferential loop
configuration.
6. A bifurcated stent as defined in claim 1, wherein said modules
are coupled to said support wire using connectors.
7. A bifurcated stent as defined in claim 6, wherein each of said
modules, support wire, and connectors are formed from a material
sufficiently similar in composition to inhibit development of
corrosion at junctures where said modules, support wire, and
connectors join each other.
8. A bifurcated stent as defined in claim 6, further comprising
spacers disposed between adjacent connectors.
9. A bifurcated stent as defined in claim 8, wherein said spacers
and said connectors are formed of the same material and define a
substantially continuous region of high radiopacity when visualized
radiographically.
10. A bifurcated stent as defined in claim 4, wherein said
serpentine wire and said support wire have a different
malleability.
11. A bifurcated stent as defined in claim 4, wherein said
serpentine wire is formed from a material belonging to the group
comprising annealed stainless steel, titanium alloys, nickel gold
alloys, nickel chromium alloys, and titanium chromium alloys.
12. A bifurcated stent as defined in claim 1, wherein said first
side branch comprises a plurality of modules and said second side
branch comprises a plurality of modules.
13. A bifurcated stent as defined in claim 1, wherein said support
wire of said first side branch comprises an extension of said
support wire of said main body and said first side branch is
coupled to said main body through said support wire.
14. A bifurcated stent as defined in claim 13, wherein each of said
modules of said first side branch are coupled to said support
wire.
15. A bifurcated stent as defined in claim 14, wherein said modules
of said first side branch are coupled to said support wire using
connectors.
16. A bifurcated stent as defined in claim 14, wherein each of said
modules of said first branch is formed from a serpentine wire
having a plurality of elongate segments alternated with shorter
connective bends.
17. A bifurcated stent as defined in claim 16, wherein said
serpentine wire has free terminal ends attached to a connector to
secure each of said modules in its closed circumferential loop
configuration.
18. A bifurcated stent as defined in claim 1, wherein each of said
modules of said main body is coupled to at least two support wires
and one of said at least two support wires extends to said first
side branch to form said support wire of said first side branch and
another of said at least two support wires extends to said second
side branch to form said support wire of said second branch.
19. A bifurcated stent as defined in claim 1, wherein the stent is
coated with a protective material.
20. A bifurcated stent as defined in claim 19, wherein said
protective material comprises carbon.
21. The bifurcated stent of claim 18, wherein said support wires
extending from said main body to said first side branch and said
second side branch each terminate at a first module of each of said
first side branch and said second side branch and said first and
second side branches are coupled to each other utilizing a third
support wire coupled to a plurality of modules of said first and
second side branches and extending
into said apex section of the stent.
Description
BACKGROUND OF THE INVENTION
A number of medical procedures involve or can be supplemented with
the placement of an endoluminal prostheses, commonly referred to as
a stent, that can be implanted in a lumen, such as a blood vessel
or other natural pathway of a patient's body. Such stents typically
define a generally tubular configuration, and are expandable from a
relatively small diameter (low profile) to an enlarged diameter.
While in its low profile configuration, the stent is advanced
endoluminally, by a delivery device, through the body lumen to the
site where the stent is to be placed. The stent then can be
expanded to a larger diameter to firmly engage the inner wall of
the body lumen. When the stent is delivered satisfactorily the
delivery device is removed, leaving the implanted stent in place.
In that manner, the stent may serve to maintain open a blood vessel
or other natural duct, the functioning of which had become impaired
as a result of a pathological or traumatic occurrence.
Among the medical procedures in which stents have had increasing
use is in connection with percutaneous transluminal angioplasty
(PTA), and particularly percutaneous transluminal coronary
angioplasty (PTCA). PTA and PTCA involve the insertion and
manipulation of a dilating catheter through the patient's arteries
to place the dilatation balloon of the catheter within an
obstructed portion (stenosis) of a blood vessel. The balloon is
expanded forcibly within the obstruction to dilate that portion of
the blood vessel, thereby restoring blood flow through the blood
vessel. Among the more significant complications that may result
from such angioplasty is when the dilated site becomes obstructed
again, for example, by restenosis. By placing a stent within the
blood vessel at the treated site, the tendency for such restenosis
may be reduced.
Stenoses may often develop in the branching region of a patient's
blood vessel. Treatment of a stenosis in the branched region may
present numerous additional difficulties in the design of devices
to dilate stenoses at the branched region. Techniques and devices
have been developed to effect a dilatation at a branched region
such as the "kissing balloon" technique described in U.S. Pat. No.
4,896,670, or pending Bard patent "Dual Balloon System." The need
for an effective stent that can be placed at a bifurcated region
has been recognized.
SUMMARY OF THE INVENTION
The invention includes, inter alia, stents, methods for making
stents, and procedures for treating restenosis and other conditions
suitable for treatment by application of an endoluminal prosthesis.
The stents described herein can include, but are not limited to,
bifurcated stents constructed in a modular fashion and having at
least one elongate spine suitable for disposition within a vessel.
The spine can attach to a plurality of generally tubular modules to
form a longitudinally sequenced array of such modules. Each module
can define, in cooperation with its associated spine, a closed,
ring-like structure, with the modules being aligned in an array to
define a cage-like, generally tubular structure. Each of the
modules may be formed from wire and is radially expandable from a
reduced diameter, low profile configuration to an expanded diameter
profile suitable for engaging with the inner luminal surface of a
blood vessel or other body lumen. Each spine can include a
longitudinal support wire to which the modules may be individually
mounted in succession.
In one embodiment, the bifurcated stent is composed of three
sections, one main body and two side branch sections. Each section
can define a single tubular configuration having its own array of
modules connected to and extending along at least one spine. The
main body of the stent is connected to the two side branch sections
by means of one or more spines and/or by means of the modules.
In one practice, the stents described herein can be placed onto a
dual balloon catheter delivery system, or onto two balloon
catheters and, while in the low profile configuration, can be
advanced to a bifurcated vessel. A delivery system incorporating a
protective retractable covering sleeve over the stent may also be
employed. The stent can be deployed by applying a radial force to
the modules, optionally by inflation of a balloon catheter.
Among the objectives of the invention is to provide an easily
placable bifurcated endovascular stent.
Another object of the invention is to provide a bifurcated stent
that can be placed in the coronary arteries as well as other
branched vessels.
Another object of the invention is to provide a bifurcated stent
that can be tailored to the vascular anatomy of the patient in whom
the device is to be implanted.
Another object of the invention is to provide a bifurcated stent of
which a region of the bifurcate stent, for example the region
nearest the apex region of the branching vessel, can be
independently tailored to suit the particular vessel.
A further object of the invention is to provide a bifurcated stent
having good radiographic characteristics to facilitate placement
and subsequent visualization of the stent.
Another object of the invention is to provide a bifurcated stent
construction that is modular.
Another object of the invention is to provide a bifurcated stent
that can be used as a scaffold for a PTFE, or other, graft for
peripheral & coronary applications.
DESCRIPTION OF THE DRAWINGS
The foregoing and other objects and advantages of the invention
will be appreciated more fully from the following description
thereof, with reference to the accompanying drawings wherein:
FIG. 1(a) is a side illustration of one bifurcate stent in a
deployed configuration.
FIG. 1(b) provides an oblique perspective of one bifurcate stent in
a deployed configuration.
FIG. 2 is a side illustration of one bifurcate stent in a deployed
configuration with an alternative arrangement of spines in the side
branches.
FIG. 3 is a side illustration of one bifurcate stent in a deployed
configuration with a modified apex section to provide more wall
coverage at the apex section of the branched vessel.
FIG. 4 is a diagrammatic illustration of a stent of the type
depicted in FIGS. 1-3 carried on two balloons while in a low
profile configuration.
FIGS. 5(a)-(c) are diagrammatic illustrations of modules of the
stent illustrating a possible connection to a support wire and some
examples of different module configurations.
FIGS. 6(a)-(c) illustrate, diagrammatically, one manner in which a
bifurcate stent can be deployed using a dual balloon
arrangement.
FIGS. 7(a)-(e) illustrate, diagrammatically one technique for
deploying a bifurcate stent by operation of separate balloon
catheters.
DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS
FIGS. 1(a)-(b) illustrate one type of modular endoprosthesis, a
stent, that may be employed in practicing the invention. In
particular, FIG. 1(a) depicts a stent having a main body 3 formed
of modules 11 and connectors 9, and side branches 5 formed of side
branch modules 7, and connectors 9. The depicted stent includes two
support wires 6, each of which extends substantially from the
proximal end to the distal end of the stent. For clarity, the terms
"proximal" and "distal" can be understood from the stent of FIG.
1(a) and from the definition that the main body 3 is proximal of
the side branches 5. FIG. 1(a) further depicts that each of the
support wires 6 extend along the sidewall of the main body 3,
branching off at the apex formed where the side branches 5 join the
main body 3. FIG. 1(a) further depicts that each support wires 6
attaches to a respective one of the side branches 5, and continues
on distally, to provide a spine along the sidewall of the
respective side branch 5. The support wires 6 connect the main body
3 to each of the side branches 5. Optionally, one or more of the
support wires 6 can be formed from a flexible or resilient
material, thereby allowing the side branches 5 to be brought
together from the opened configuration of FIG. 1(a), to the closed
configuration depicted in FIG. 4. Additionally, a resilient as
support wire 6 can be biased in the open configuration of FIG.
1(a), such that the support wires 6 will tend to move the stent
from the closed configuration of FIG. 4, to the open configuration
of FIG. 1(a).
The endoprosthesis may be considered to define a cage-like tubular
arrangement formed from wire-like components and having a main body
section 3 and two side branch sections 5. The stent depicted in
FIGS. 1(a)-(b) is constructed from a plurality of individual
modules, containing main body modules 11 and side branch modules 7
connected to each other along at least one spine that may be
considered to include a longitudinal support wire 6 and connectors
9. The modules 7 and 11 are expandable from a contracted, low
profile configuration, to facilitate placement of the stent in the
body lumen, to an enlarged diameter in which the modules can be
brought into firm engagement with the inner surface of the walls of
the body lumen to maintain the body lumen open to facilitate blood
flow. In the one optional embodiment, the modules are expandable
inelastically. The radially expandable generally tubular modules 7
and 11 are mounted and aligned in longitudinally sequenced array on
the support wire 6 by a connector 9 associated with each of the
modules 7 and 11. As detailed in FIG. 5(b), the modules 7, when
mounted on a support wire 6, may be considered to define a virtual
peripheral surface 12, that, in transverse cross-section, is in the
form of a virtual closed curve or loop 8 about the longitudinal
axis 2. Likewise the modules 11 in the main body 3, when mounted on
at least one support wire 6, may also be considered to define a
virtual peripheral surface.
Each module 7 and 11 can be formed from a wire 13 shaped and
configured to enable radial expansion of the cylindrical peripheral
surface 12. The module may be formed by first forming the wire 13
into a flat serpentine configuration and then wrapping the
serpentine wire into its looped configuration. The terminal ends 16
of the serpentine wire 13 are free. The free ends 16 of the wire 13
may be attached to each other and to the support wire 6 by the
connector 9. The serpentine arrangement of each of the modules may
be considered to include a series of elongate segments alternated
with and connected by bends that may be curved (e.g., circular) or
may comprise shorter connective segments 15 connected to the
elongate segments 14 at cusps 17. The connective bends between the
longitudinal segments 14 may lie along and define a locus of the
closed loop 8. Preferably, the wire 13 is formed so that the
arrangement of bends will be uniformly circumferentially spaced
about the virtual closed loop 8 to provide the modules 7 and 11
with uniform strength in directions transverse to the support wire
or wires 6.
As illustrated in FIG. 5(b) when the modules are in their low
profile, unexpanded configuration, the bends 15, 17 that define the
connection between adjacent longitudinal segments are such that the
elongate segments 14 will lie substantially parallel to each other,
defining an angle close to zero degrees. The angle will increase
when the module is expanded, as shown in FIG. 5(a). The
configuration of the connective bends, including the cusps 17 may
be varied to vary the angle or to vary their number
circumferentially about the closed loop 8 to vary the
characteristics of the modules 7 and 11, including varying its
resistance to compressive radial loads such that the endoprosthesis
can further be tailored and made to conform ideally to the specific
body lumen in which it is to be implanted.
By way of illustrative example only, a stent may be provided to
include modules 7 formed from wire having a diameter of about 0.15
millimeter with elongate segments 14 (not including the connective
bends between adjacent segments 14) of a length of about 1.8
millimeters. When the connective bends between adjacent elongate
segments 14 are smoothly curved, they may have a radius of about
0.15 millimeter before expansion. A stent having the foregoing
dimensions can be expected to be expandable to diameters between
about 2.5 to about 4.0 millimeters without excessive expansion, and
that such stent exhibits substantial resistance to radial collapse
that can be well above the maximum radial compressive loads and can
be expected to be imposed on the stent by contraction of an artery
having a luminal diameter of about 2.5 to about 4.0
millimeters.
Again by way of illustrative example only, a stent may be provided
to include modules 11 formed from wire having a diameter of about
0.15
millimeter with elongate segments 14 (not including the connective
bends between adjacent segments 14) of a length of about 2.7
millimeters. When the connective bends between adjacent elongate
segments 14 are smoothly curved, they may have a radius of about
0.15 millimeter before expansion. A stent having the foregoing
dimensions can be expected to be expandable to diameters between
about 3.0 to about 5.5 millimeters without excessive expansion, and
that such stent exhibits substantial resistance to radial collapse
that is well above the maximum radial compressive loads and can be
expected to be imposed on the stent by contraction of an artery
having a luminal diameter of about 3.0 to about 5.5
millimeters.
In one embodiment, the connectors 9 may be constructed to be
mounted on the longitudinal support wire 6 by threading them on the
wire 6. The connector 9 preferably may comprise a ring that defines
sufficient internal space to receive and circumscribe the free ends
16 of the wire 13 while also permitting firm connection of the ring
to the longitudinal support wire 6. The connector 9, free ends 16
of the wire and support wire 6 may be firmly connected by means of
a permanent deformation, for example, by crimping, or may be
attached to each other by spot welding. When assembled using laser
spot welding, it is preferred that the terminal portions 16 of the
module 7 or 11 are first welded to the connector(s) 9 and the
connector(s) 9 then is welded to the support wire 6. In some
instances, it may be desirable to modify the stent so that one or
more of the modules (but typically not the endmost modules) are not
securely attached to the support wire but, instead, are permitted
some freedom of sliding movement along the support wire. This may
enable making of a final adjustment to the position of the module
after the device has been placed in the patient's blood vessel,
should that be desired.
Connector 9 may be in the form of a relatively short segment of a
tube receptive to the support wire 6 and the free ends 16 of the
modules 7 and 11. The internal surface of the connector 9 may be
contoured to closely match the contour defined by the support wire
6 and free ends 16 that pass through the connectors 9, thus in
effect preforming the connector.
The foregoing construction enables a stent to be specially
assembled to conform precisely to the specific anatomy of the
patient in whom the stent is to be placed. The modules can be
positioned as desired along the support wire 6 and can be secured
in that configuration. The support wire 6 may be selected to
provide the desired degree of longitudinal flexibility and may be
made from wire that is extremely flexible to aid in each of
positioning of the device. With the foregoing construction in which
the stent has at least one independent support wire 6 in each
section, the degree of stiffness or flexibility of the support wire
can be selected independently of the wire from which the tubular
modules 7 are formed. The support wire 6 may be highly flexible to
aid the stent to be carried through tortuous vessels, such as
coronary arteries.
It should be understood that although the presently preferred
embodiment of the invention incorporates a metal support wire 6
(e.g., stainless steel), the modular construction of the invention
enables a fabrication of a stent in which the support wire may be
formed from nonmetallic materials, such a polymeric materials, for
example, nylon. Other mechanically and biologically suitable
classes of materials may be selected, including materials from
among those that are biologically absorbable into the tissue of the
vessel wall over time. With a bioabsorbable support wire 6, it
should be selected to maintain its desirable mechanical
characteristics for a sufficient time to enable the modules 7 to
become firmly embedded in the vessel wall. Thus, the modular
construction of the invention provides a substantially increased
range of materials and properties for the individual components,
each being selected to provide optimum results.
Connectors 9, especially when assembled about the two end segments
16 of the modules 7 and 11 and the support wire 6, present a
significantly greater mass than that of the wire 13 from which the
modules are fashioned. Thus, the region of the spine that includes
the Connectors 9 will present substantially greater radiopacity
than that presented by the wire 13 of the associated module. The
substantially increased radiopacity of the connected region
enhances substantially the radiographic control of the
endoprosthesis 1(a)-(c) during implantation. It also enables the
prosthesis to be observed radiographically at a later time without
requiring use of ultrasound procedures. The configuration of the
stent enables the tubular frame 10 to be constructed to have a high
mechanical strength while enabling expansion of the device between
its low profile and maximum expanded alloys, and titanium-chromium
alloys.
The support wire 6 and modules may be treated and formed to vary
the mechanical and functional characteristics independently of each
other to obtain a desired configuration adapted to treat the
anatomy of a specific patient. For example, the wire 13 from which
the module is formed may be subjected to an annealing heat
treatment to control the malleability of the wire.
Also among the characteristics of the invention is the manner in
which the tubular modules 7 protect the balloon of a balloon
catheter 4 (FIG. 4) used in the placement of the endoprosthesis
1(a)-(c). When the device if mounted on the folded balloon of the
catheter and is in its low profile phase adapted for delivery, the
elongate segments 14 will be disposed in close substantially
parallel proximity to each other circumferentially about the
balloon. Additionally, to the extent that the individual tubular
modules can be arranged in close longitudinal proximity to each
other the balloon can be fully protected within the stent
longitudinally as well as circumferentially. After the device and
catheter 4 have been navigated to locate the deployment site,
expansion of the device can cause the elongate segments 14 to
spread and expand circumferentially along the walls to the body
lumen to wipe against the walls and smooth surface roughness that
may be present including, particularly, smoothing of sharp or hard
regions that otherwise could damage the balloon and possibly result
in balloon puncture. As the segments 14 of the module wipe against
the walls of the passage, they effect a significant shearing
action.
It may be noted that the main body 3 and side branch 5 sections may
be constructed with multiple spines. FIG. 5(c) illustrates an
arrangement in which the module is constructed using two connectors
9 and support wires 6 circumferentially spaced about the virtual
periphery 12, so as to create two spines. In this embodiment, each
of the wires 13 of the modules 11 is formed to circumscribe about
180.degree. of the loop defined by the module such that they can
cooperate to define the generally cylindrical configuration. The
connectors 9 shown in FIG. 5(c) may be pre-formed into a shape as
shown so as to aid placement of the wire 13 during manufacture.
FIG. 6 illustrates a possible technique to deploy the stent, shown
here as a general outline 24 to simplify the diagram and aid
viewing, using a dual balloon arrangement. Two guide wires 19 are
positioned in the bifurcated vessel 18 by means of the known prior
art. This is illustrated in FIG. 6(a). The bifurcated stent is
crimped onto the dual balloons to obtain the low profile state and
the two balloons of the dual balloon catheter with the crimped
stent are advanced over the guide wires to the bifurcated vessel as
depicted in FIG. 6(b). The system can be advanced through a guiding
catheter (not shown) to the site of the bifurcated vessel by any
suitable system or method known in the art. The dual balloon
catheter is now used to expand the stent to its deployed
configuration by applying a radial force on the modules of the
stent by means of the two balloons 25, as depicted in FIG. 6(c).
The balloons 25 are now deflated and can be removed along with the
guide wires 19 to leave the stent 24 in its deployed
configuration.
FIG. 7 illustrates one possible technique to deploy the stent,
again shown here as a general outline 24 to simplify the diagram
and aid viewing, using standard balloon catheters. Two guide wires
19 are positioned in the bifurcated vessel 18 by any means known in
the art. The stent is crimped down onto two separate balloons, one
balloon 21, being longer than the other 22. The bifurcated stent is
crimped onto the two balloons 21 and 22 to obtain the low profile
state and the two balloons 21 and 22 with the crimped stent are
advanced over the guide wires to the bifurcated vessel 18 as
depicted in FIG. 7(a). The system can be advanced through a guiding
catheter to the site of the bifurcated vessel by any suitable
system or method known in the art. The two balloon catheters is now
used to expand the stent 24 to its deployed configuration by
applying a radial force on the modules of the stent 24 to its
deployed configuration by applying a radial force on the modules of
the stent 24 by means of the two balloons 21 and 22 sized to fit
the side branch vessels 28, as depicted in FIG. 7(b). The balloons
21 and 22 are now deflated and can be removed. A third balloon 23,
sized to fit the main branch vessel 27 can now be inserted over one
of the guide wires 19, as shown in FIG. 7(d). The balloon 23 can
now be deflated and can be removed along with the guide wires 19 to
leave the stent 24 in its deployed configuration, as shown in FIG.
7(e).
If desired, the wires embodied in the stent 1(a)-(c) may be coated
with a protective material such as carbon or with an anticoagulant
substance such as heparin.
In a further alternative embodiment, the stent may be expandable by
other means, for example, by forming the module 7 from a shape
memory alloy such as nitinol. The stent may be provided with
electrical resistance heaters to generate sufficient heat to induce
thermally controlled expansion of the shape memory alloy module. A
delivery system could be used to position the stent in the
bifurcated vessel which would facilitate expansion of the stent
after placement.
If felt necessary after deployment, post dilatation with balloons
tailored to the artery could follow the stent deployment.
It should be understood that the foregoing description of the
invention is intended merely to be illustrative thereof and that
other embodiments, modifications and equivalents will be apparent
to those skilled in the art without departing from its
principles.
* * * * *